For starters, you can try West Marine, Lakewood Yacht Service and Palmer Power for Teleflex/Morse cables in common lengths. I personally use Pro-X cables from Glendenning
and get them straight from the factory in a couple of days. Very high quality, fairly priced and made in the USA. These cables are popular with the sportfish and go-fast crowd. They are low friction and have very low lost motion. Precision cables make your controls very accurate and positive. I have used them for years on everything from sailboats to go-fast boats, and now, even on my little trawler. I have never had to replace one.